Vapour power plant with hermetic turbogenerator

ABSTRACT

The vapour power plant with hermetic turbogenerator is claimed, such plant provided with the main thermal cycle that works with the low boiling point fluid, and characterized by an additional, internal working fluid cycle that serves to lubricate the slide bearings contained in said hermetic turbogenerator, said additional working fluid cycle consisting of the slide bearings supplying piping connected to the main working fluid cycle at the main cycle pump outlet, of the slide bearings housing, of the return piping that directs the main portion of the working fluid liquid from said slide bearing housing to the working fluid buffer container, and of the emergency slide bearings supply piping that connects said working fluid buffer container, through the emergency slide bearing supply pump, with said slide bearings supply piping, whereby non-return valves are provided before connection point of said slide bearings supply piping and said emergency slide bearings supply piping.

BACKGROUND AND GENERAL DESCRIPTION

The invention relates to the vapor power plant with hermeticturbogenerator. The vapor power plant is based on the Organic RankineCycle (ORC), i.e. on the thermal power plant cycle that works with lowboiling point fluids instead of water.

One known hermetic turbogenerator to work in vapor power plants that arebased on the thermal power plant cycle with low boiling point fluids isdisclosed in the Polish Patent Application P 390472. This hermeticturbogenerator consists of an electric generator and of a vapour turbinethat are both placed in the hermetic casing of the turbogenerator. Theelectric generator is cooled with the working fluid vapour that has beenexpanded in the vapour turbine. The inlet of the high pressure vapour ofthe working fluid is arranged in the hermetic casing in front of thevapour turbine, and the outlet of the expanded vapour is positioned inthe hermetic casing behind the electric generator. A system of powergeneration known from the description of the invention GB1083239 isbased on thiophenc as the cycle working fluid that is heated andevaporated in a vapour generator, expanded in a turbine, cooled andcondensed in a condenser and supplied back to the vapour generator. Inthat invention, thiophene is used to lubricate the turbine bearings. Theinvention does not relate to the hermetic generator and does notincorporate any piping system attached to the turbine bearings to returnthe lubricating fluid as its liquid phase. A portable micro power plantoperating with mercury vapour as the working fluid is known from theinvention U.S. Pat. No. 2,961,550. The system incorporates a hermeticturbogenerator and its internal bearings are lubricated by the workingfluid liquid that is, under low pressure, supplied from the condenser.The invention does not relate to the turbogenerator in which theelectric generator is cooled with the working fluid vapour, and can notbe applied to the cases where low boiling point fluids are used as thecycle working fluids. A power plant known from the invention US20110047958 contains a vapour turbine with an electric generator, anevaporator, a condenser, a cycle pump, and is working with HFE as thecycle working fluid that is mixed with fluoric oil acting as lubricantfor the bearings. A fraction of the working fluid with a high content ofthe lubricant is extracted from the evaporator and is used to lubricatethe rolling bearings. A method to secure the lubrication of the highspeed turbogenerator bearings is known from the internationalpublication WO 9205342. In this method, for the case of the cycleworking fluid pump emergency stoppage, the ORC turbogenerator rotorslide bearings are lubricated with the cycle working fluid supplied fromthe lower part of the evaporator upon the principle that the evaporatorpressure would then increase. The solution does not apply to thehermetic turbogenerator in which the electric generator is cooled withthe working fluid vapour, and it does not properly regard the thermalprocess inertia that excludes the rotor bearings emergency supply. Avapour power plant with the hermetic turbogenerator is known from thePolish Patent Application P 390472. In that solution, the electricgenerator placed together with the vapour turbine inside a hermeticcasing is cooled with the expanded working fluid vapour. The inlet ofthe high pressure vapour is located in the hermetic casing upstream tothe turbine inlet. The outlet of the expanded vapour is located in thehermetic casing downstream to the electric generator position. Theexpanded vapour of the working fluid flows around the electric generatorand carries away heat emitted by the generator.

The goal of the present invention is, for the standard ORC power plantof moderate power output, to provide a solution that (1) enables aneffective lubrication of the slide bearings enclosed in the hermeticturbogenerator that is cooled with the working fluid vapour of the powerplant cycle, that (2) provides effective protection of theturbogenerator bearings lubrication in case of the power plant cycleemergency stoppage, that (3) works without lubricants other than thecycle working fluid and that (4) works without the effect of loweringthe power plant efficiency.

BRIEF DESCRIPTION OF THE DRAWING

In the accompanying drawing:

FIG. 1 is a schematic diagram showing main components of a vapour powerplant.

According to the present invention, the ORC power plant contains themain thermal cycle of the working fluid, whereby that cycle works withthe low boiling point working fluid and extends from the preheater andevaporator through the vapour turbine, the latter being placed togetherwith the electric generator in a common hermetic casing to form thehermetic turbogenerator, next through the condenser, the working fluidbuffer container, the main cycle pump and back to the preheater. Theelectric generator is cooled by the expanded vapour of the workingfluid, whereby the high pressure vapour inlet is located in the commonhermetic casing upstream to the turbine and the expanded vapour outletof the common hermetic casing is located downstream to the electricgenerator position. By virtue of the present invention, the ORC powerplant described above contains an additional, internal cycle of theworking fluid that serves for the slide bearing lubrication and thatconsists of the slide bearings supplying piping, the latter beingattached to the main working fluid cycle downstream to the main cyclepump, of the slide bearings housing and of the return piping whichdirects the main portion of the working fluid liquid from the slidebearings to the working fluid buffer container and back to the maincycle pump. The remaining portion of the working fluid liquid that, inthe slide bearings labyrinth seals, expands to the vapour phase isdirected from the hermetic casing to the condenser, jointly with theworking fluid vapour having been expanded in the turbine. An additional,emergency supplying piping that incorporates an emergency working fluidpump then connects the working fluid buffer container and the slidebearing supplying piping. The emergency pump is activated in case ofcycle pump failure during the power plant operation. Both the slidebearing supplying piping and emergency supplying piping includenon-return valves directly prior to piping connection point.

The advantage of the present invention lies in continuous, long lastinglubrication of the turbogenerator slide bearings, in contrast to therelevant situation with the known hermetic turbogenerator. Thisadvantage effectively reduces maintenance requirements in cases wherethe ORC power plant with hermetic turbogenerator is used in realindustrial conditions. In line with the present invention, the relevantORC power plant solution enables the working fluid liquid as lubricantto be supplied to the slide bearings at much higher pressure than thatof the slide bearings exterior. The homogeneity and cleanliness of theworking fluid, thus the unlowered efficiency of the power plant, are theadvantage of the solution with the working fluid as lubricant for thehermetic turbogenerator slide bearings, when no other lubricant isneeded. There is then no need to seal the bearings to avoid mixing oflubricant with the working fluid vapour. Complicated systems of thelubricating oil sequestration and separation used in standard bearingarrangements are eliminated. Moreover, as operation of such oilsequestration and separation systems is not perfect, lubrication of theturbogenerator bearings with the working fluid eliminates the need toperiodically replace the working fluid in the power plant cycle asresult of the working fluid contamination that worsens the power plantefficiency. An essential improvement according to the present inventionis provided by the solution that protects the turbogenerator slidebearings against consequences of the power plant cycle pump failure.

The invention is presented in more detail through a description of itspreferred embodiment supported by a drawing that shows the vapour powerplant incorporating the additional, internal working fluid cycle for theturbogenerator slide bearing lubrication.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The main working fluid cycle of the ORC power plant converts lowtemperature heat into mechanical energy that is then transformed intoelectrical energy. A special working fluid, mostly of organic nature,circulates in that cycle. The working fluid liquid that flows throughthe preheater 6 and next through the evaporator 5 extracts heat from thesupplying energy carrier 9. The working fluid being then in form of thehot working fluid vapor is directed to the turbine 2 that, due to theworking fluid vapor expansion, generates mechanical power. The turbine 2drives the electric generator 3 by means of the common shaft connectingthe turbine and generator rotors. Both the turbine 2 and electricgenerator 3 are placed in the common turbogenerator casing 1. Theelectric generator 3 is cooled with the expanded working fluid vapourcoming from the turbine outlet. The expanded working fluid vapour leavesthe turbogenerator casing 1 and is directed, via the piping 13, to thecondenser 7 where it is cooled and condensed to liquid phase with helpof the cooling fluid 11. The resulting working fluid liquid flows fromthe condenser 7 through the buffer container 14 to the main cycle pump 8that raises the working fluid pressure. The pressurized working fluidliquid is then directed to the preheater 6 and the whole working fluidcirculation is repeated.

The main working fluid cycle is supplemented by an additional, internalworking fluid cycle that serves for lubrication of the turbogeneratorslide bearings. The slide bearings supply piping 12 is connected to theoutlet of the main cycle pump 8 and is used to supply the pressurizedworking fluid liquid to the slide bearings housing 4. The pressurizedworking fluid liquid lubricates the turbogenerator slide bearings and,at the same time, its pressure drops. Then, the main portion of theworking fluid liquid is from the slide bearings housing returned to thebuffer container 14 by using the return piping 10. The remaining portionof the working fluid liquid that, in the labyrinth seals of the slidebearings housing, expands to the vapour phase is, together with theworking fluid vapour of the main cycle, directed to the condenser 7. Theslide bearings supply piping 12 is additionally connected with theworking fluid buffer container 14 via the emergency supply piping 18that incorporates the emergency supply pump 15. Both the slide bearingssupply piping 12 and the emergency supply piping 18, upstream to theirconnection point, are equipped with non-return valves, 16 and 17respectively. In case of the main cycle pump failure, or when theworking fluid pressure in the main cycle unexpectedly drops because ofother reasons, the power plant control system decouples the electricgenerator from the electric network and activates the emergency supplypump 15 to allow for a safe stoppage of rotating elements of theturbogenerator.

1. A vapour power plant with a hermetically sealed turbogenerator,comprising a main thermal cycle that works with a low boiling pointfluid and extends consecutively from a preheater and evaporator throughthe hermetically sealed turbogenerator consisting of the vapor turbineplaced together with the electric generator within a common hermeticcasing, next through a condenser, working fluid buffer container, a maincycle pump and back to said preheater, whereby said electric generatoris cooled with the expanded vapour from the said turbine outlet, and aninlet of the high pressure working fluid vapour into said commonhermetically sealed casing is located in front of said turbine and theoutlet of the expanded working fluid vapour is in said common hermeticcasing located behind said electric generator, wherein an additional,internal working fluid cycle that serves to lubricate the slide bearingscontained in said hermetic turbogenerator and that consists of the slidebearings supplying piping (12) connected to the main working fluid cycleat an outlet of said main cycle pump (8), of the slide bearings housing(4), of the return piping (10) that directs the main portion of theworking fluid liquid from said slide bearing housing (4) preferably tosaid working fluid buffer container (14), and of the emergency slidebearings supply piping (18) that connects said working fluid buffercontainer (14), through the emergency slide bearing supply pump (15),with said slide bearings supply piping (12), whereby said slide bearingssupply piping (12) and said emergency slide bearings supply piping (18)contain non-return valves (16) and (17), respectively.
 2. A method forproducing vapour with a hermetic turbogenerator comprising working witha main thermal cycle; employing low boiling point fluid; and extendingconsecutively from a preheater and evaporator through the hermeticturbogenerator; placing a vapour turbine together with an electricgenerator within a common hermetic casing, next through the condenser,working fluid buffer container, main cycle pump and back to saidpreheater; cooling said electric generator with an expanded vapour fromthe said turbine outlet and the inlet of the high pressure working fluidvapour into said common hermetic casing which is located in front ofsaid turbine and the outlet of the expanded working fluid vapour is insaid common hermetic casing located behind said electric generator,wherein an additional, serving to lubricate the slide bearings containedin said hermetic turbogenerator with an additional internal workingfluid cycle; consisting of slide bearings supplying piping (12)connected to the main working fluid cycle at the outlet of said maincycle pump (8), of the slide bearings housing (4), of the return piping(10); directing the main portion of the working fluid liquid from saidslide bearing housing (4) preferably to said working fluid buffercontainer (14), and of the emergency slide bearings supply piping (18)that connects said working fluid buffer container (14), through theemergency slide bearing supply pump (15), with said slide bearingssupply piping (12), whereby said slide bearings supply piping (12) andsaid emergency slide bearings supply piping (18) contain non-returnvalves (16) and (17), respectively.
 3. The vapour power plant withhermetic turbogenerator, with the main thermal cycle that works with thelow boiling point fluid and extends consecutively from the preheater andevaporator through the hermetic turbogenerator consisting of the vapourturbine placed together with the electric generator within a commonhermetic casing, next through the condenser, working fluid buffercontainer, main cycle pump and back to said preheater, whereby saidelectric generator is cooled with the expanded vapour from the saidturbine outlet and the inlet of the high pressure working fluid vapourinto said common hermetic casing is located in front of said turbine andthe outlet of the expanded working fluid vapour is in said commonhermetic casing located behind said electric generator, wherein anadditional, internal working fluid cycle that serves to lubricate theslide bearings contained in said hermetic turbogenerator and thatconsists of the slide bearings supplying piping (12) connected to themain working fluid cycle at the outlet of said main cycle pump (8), ofthe slide bearings housing (4), of the return piping (10) that directsthe main portion of the working fluid liquid from said slide bearinghousing (4) preferably to said working fluid buffer container (14), andof the emergency slide bearings supply piping (18) that connects saidworking fluid buffer container (14), through the emergency slide bearingsupply pump (15), with said slide bearings supply piping (12), wherebysaid slide bearings supply piping (12) and said emergency slide bearingssupply piping (18) contain non-return valves (16) and (17),respectively.